The present invention relates to an IC temperature sensor used for electrical products.
An IC temperature sensor which can be formed by the same process as CMOS and which NPN bipolar transistors are connected in a Darlington circuit is described in Japanese Patent No. S59-47467. FIG. 5 is a circuit diagram of NPN bipolar transistors connected in a double Darlington circuit and a constant current circuit is connected to an emitter of a transistor 102. This circuit detects the sum Vout of a voltage between a base and an emitter of a transistor 101 and voltage between a base and emitter of the transistor 102. An example of double collector construction applied to transistor 102 of FIG. 5 is shown in FIG. 13. In the above IC temperature sensor, current I1 between base and emitter of first transistor 101 is 0.1/xcex2 of current I2 between base and emitter of second transistor 102. As it is so small, the IC temperature sensor has had a problem to be sensitive to noise. Here, xcex2 is current-amplification factor of transistor 102. Further, the IC temperature sensor has had a problem that current-amplification factor xcex2 deviated, I1 deviated, and detecting voltage Vout deviated much.
Although a construction of transistor for making xcex2 small is shown, the above problem has not been solved because xcex2 does not become small, only about 10. When more than triple transistors are connected, deviation of detecting voltage Vout is large. The triple transistors is the limit practically.
The IC temperature sensor has had another problem that current consumption of the IC became large because large current must flow through the last transistor to make stable by flowing some current through the first transistor. Because of the problem, the area of the last transistor becomes large and the cost of the IC becomes high.
The IC temperature sensor has had a problem that current flowing through transistors except last transistor changed according to temperature and the more the connection of transistor were, the worse the linearity of detecting voltage Vout became.
The IC temperature sensor has had a problem that processes increase because different impurity concentration regions such as base region and emitter region of bipolar transistors, and well region and each source drain region of N and P types of CMOS had to be formed.
The IC temperature sensor has had a problem that temperature linearity of detecting voltage became bad because there was a difference between mobility temperature characteristics of well region of CMOS transistor assuming temperature characteristics of a constant current circuit and mobility temperature characteristics of base region assuming temperature characteristics of a bipolar transistor. The IC temperature sensor has had a problem that detecting voltage predetermined current became small by making impurity concentration of base region high and constant current for gaining the specified detecting voltage became large
The IC temperature sensor has had a problem that effective area of junction between base and collector was influenced by diffusion distance of minority carrier in base, and xcex2 was easy to deviate.
Therefore, in order to solve the problems, the object of the present invention is to provide an IC temperature sensor which is low cost, small current consumption, small deviation of detecting voltage, and superior anti-noise characteristics and linearity of detecting voltage.
The semiconductor temperature sensor of the invention comprises plural bipolar transistors connected in Darlington circuit, and each emitter electrode of the bipolar transistors is connected to a constant current source.
In this construction, voltage between base and emitter of each bipolar transistor is determined by current of constant current source connected and diode characteristics between base and emitter if current-amplification factor of bipolar transistor is large to a certain extent. Therefore, when the sum of voltage between base and emitter of all bipolar transistors is picked up as the output, temperature output characteristics being small in deviation is gained. The semiconductor temperature sensor of the invention comprises plural bipolar transistors connected in Darlington circuit, and a space between base diffusion layer of the bipolar transistor and chip edge of IC semiconductor temperature sensor is more than 20 xcexcm. The semiconductor temperature sensor comprises plural bipolar transistors connected in Darlington circuit, and a diffusion layer of electric conductor type differing from a semiconductor substrate is formed between base diffusion layer of said bipolar transistor and chip edge of IC semiconductor temperature sensor. To the diffusion layer, a voltage is supplied like that junction with the semiconductor substrate makes reverse bias.
In this way, minority carrier generated by lattice defect in chip edge at high temperature becomes difficult to reach base region of the bipolar transistor. Therefore, extra current is added to emitter current of each transistor at high temperature, and output temperature characteristics keeps linear.
The IC temperature sensor comprises plural bipolar transistors connected in Darlington circuit, each emitter electrode of plural bipolar transistors is connected to the current source, and voltage of the respective emitter electrode is picked up as output. In this way, plural output voltages plural sensibilities are gained from the IC temperature sensor.
The IC temperature sensor of the invention comprises plural bipolar transistors connected in Darlington circuit, each emitter electrode of plural bipolar transistors is connected to the current source, and output voltage or sensibility of the IC temperature sensor becomes adjustable by changing current of current source by trimming.
Output voltage of the IC temperature sensor is the sum of voltage between base and emitter of plural bipolar transistors. Sensitivity of the IC temperature sensor is the sum of variation per unit temperature of voltage between base and emitter of plural bipolar transistors. When current flowing through emitter of the bipolar transistor changes, voltage between base and emitter changes. Therefore, output voltage can be adjusted by trimming the current.
When current flowing through emitter of the bipolar transistor changes, variation per unit temperature of voltage between base and emitter changes. Therefore, sensibility can be adjusted by trimming the current.